1. Field of the Invention
The present invention relates to a retainer ring and a polishing machine having the same.
2. Description of the Related Art
Recently, in the process of production of devices on a semiconductor substrate, a chemical mechanical polishing (hereinafter, called “CMP”) method is used to flatten unevenness on surfaces generated during the production process, such as unevenness on surfaces of an interlayer insulating film, by polishing.
In CMP, a polishing machine 100 is generally used, as shown in FIG. 6.
The polishing machine 100 includes a gripping portion 101 for gripping an object to be polished (not shown), a polishing table 103 to which a polishing pad 102 is attached and a chemical supply port 104.
The gripping portion 101 includes a retainer ring 101B (see FIG. 7).
In polishing, the object to be polished is gripped by the gripping portion 101, and a polished surface thereof is pressed against the polishing pad 102 and polished. The retainer ring 101B is used to prevent the object to be polished from flying out of the gripping portion 101 and an outer circumferential portion of the object to be polished from being abnormally polished.
In polishing without use of the retainer ring, a most outer circumferential portion of the object to be polished is subject to the largest contact pressure. At this time, as shown in FIG. 8A, a deformed area A is generated by the effect in the polishing pad 102 across the width of several millimeters from the most outer circumferential portion of the object to be polished 6, resulting in a lowered pressure acting on the outer circumferential portion of the object to be polished 6. As the result, a polishing amount of the outer circumferential portion of the object to be polished 6 is reduced.
Then, using the retainer ring 101B, as shown in FIG. 8B, a surface of the object to be polished 6 in contact with the polishing pad 102 and a surface of the retainer ring 101B in contact with the polishing pad 102 are made at the same height. Further, a width of the retainer ring 101B in contact with the polishing pad 102 is set to be equal to or larger than that of the deformed area A. Moreover, to the retainer ring 101B, a predetermined pressure is applied. This can prevent the deformed area A from extending to the outer circumferential portion of the object to be polished 6, which can prevent a decrease in the polishing amount by which the outer circumferential portion of the object to be polished 6 is polished (abnormal polishing). In addition, in FIGS. 8A and 8B, the symbol “101A” shows an insert pad provided on a reverse surface of the object to be polished.
The contact of the retainer ring 101B with the polishing pad 102 polishes the retainer ring 101B, and impurities spread gradually. Using alloy material such as stainless steel for the retainer ring 101B, metal components spread over the polishing pad 102, which may adversely affect characteristics of devices to be formed on the object to be polished 6. Then, it is thought that rigid plastic is used for the retainer ring 101B. However, its mechanical strength is lower, compared with stainless steel, and the retainer ring is more deformed as the number of objects to be polished that are processed increases.
Then, as shown in FIG. 9, it was proposed that a retainer ring 105 be composed of a ring-shaped resin portion 105A provided on the polishing pad 102 side and a ring-shaped portion 105B of stainless steel or the like having a high mechanical strength (see Japanese Patent Laid-Open No. 11-291162).